Inundation, Vegetation, and Sediment Effects on Litter Decomposition in Pacific Coast Tidal Marshes
- 595 Downloads
The cycling and sequestration of carbon are important ecosystem functions of estuarine wetlands that may be affected by climate change. We conducted experiments across a latitudinal and climate gradient of tidal marshes in the northeast Pacific to evaluate the effects of climate- and vegetation-related factors on litter decomposition. We manipulated tidal exposure and litter type in experimental mesocosms at two sites and used variation across marsh landscapes at seven sites to test for relationships between decomposition and marsh elevation, soil temperature, vegetation composition, litter quality, and sediment organic content. A greater than tenfold increase in manipulated tidal inundation resulted in small increases in decomposition of roots and rhizomes of two species, but no significant change in decay rates of shoots of three other species. In contrast, across the latitudinal gradient, decomposition rates of Salicornia pacifica litter were greater in high marsh than in low marsh. Rates were not correlated with sediment temperature or organic content, but were associated with plant assemblage structure including above-ground cover, species composition, and species richness. Decomposition rates also varied by litter type; at two sites in the Pacific Northwest, the grasses Deschampsia cespitosa and Distichlis spicata decomposed more slowly than the forb S. pacifica. Our data suggest that elevation gradients and vegetation structure in tidal marshes both affect rates of litter decay, potentially leading to complex spatial patterns in sediment carbon dynamics. Climate change may thus have direct effects on rates of decomposition through increased inundation from sea-level rise and indirect effects through changing plant community composition.
Keywordscarbon cycling plant composition sea-level rise sediment temperature species richness tidal inundation
- Baldwin BG, Goldman DH, Keil DJ, Patterson R, Rosatti TJ, Wilken DH. 2012. The Jepson Manual. Vascular Plants of California. 2nd edn. Berkeley: University of California Press.Google Scholar
- Chevan A, Sutherland M. 1991. Hierarchical partitioning. Am Stat 45:90–6.Google Scholar
- Jaster T, Meyers SC, Sundberg S (eds). 2016. Oregon Vascular Plant Checklist. Amaranthaceae. http://www.oregonflora.org/checklist.php. Version 1.6.
- National Research Council. 2012. Sea-level rise for the coasts of California, Oregon, and Washington: past, present, and future. Washington D.C: The National Academies Press.Google Scholar
- Oksanen J. 2015. Multivariate analysis of ecological communities in R: vegan tutorial. http://cc.oulu.fi/~jarioksa/opetus/metodi/vegantutor.pdf. Accessed 22 Jan 2016.
- Swanson KM, Drexler JZ, Schoellhamer DH, Thorne KM, Casazza ML, Overton CT, Callaway JC, Takekawa JY. 2014. Wetland accretion rate model of ecosystem resilience (WARMER) and its application to habitat sustainability for endangered species in the San Francisco estuary. Estuaries Coasts 37:476–92.CrossRefGoogle Scholar
- Thorne KM, Dugger BD, Buffington KJ, Freeman CM, Janousek CN, Powelson KW, Guntenspergen GR, Takekawa JY. 2015. Marshes to mudflats—effects of sea-level rise on tidal marshes along a latitudinal gradient in the Pacific Northwest. U.S. Geological Survey Open-file Report 2015–1204.Google Scholar
- Thorne KM, MacDonald GM, Ambrose RF, Buffington KJ, Freeman CM, Janousek CN, Brown LN, Holmquist JR, Guntenspergen GR, Powelson KW, Barnard PL, Takekawa JY. 2016. Effects of climate change on tidal marshes along a latitudinal gradient in California. U.S. Geological Survey Open-file Report 2016–1125.Google Scholar
- Weinmann F, Zika PF, Giblin DE, Legler B. 2002+. Checklist of the vascular plants of Washington state. University of Washington Herbarium. http://biology.burke.washington.edu/herbarium/waflora/checklist.php. Accessed 30 Jan 2017.